Method for transmitting multiplexed harq feedbacks in a carrier aggregation system and a device therefor

ABSTRACT

The present invention relates to a wireless communication system. More specifically, the present invention relates to a method and a device for transmitting multiplexed HARQ feedbacks in a carrier aggregation system, the method comprising: configuring a first cell with PUCCH resource and a second cell with PUCCH resource; configuring zero or more third cells without PUCCH resource; generating a first HARQ feedback by multiplexing HARQ feedbacks of all HARQ processes of the first cell and third cells associated with the first cell; generating a second HARQ feedback by multiplexing HARQ feedbacks of all HARQ processes of the second cell and third cells associated with the second cell; and transmitting the first HARQ feedback on the first cell with PUCCH resource and the second HARQ feedback on the second cell with PUCCH resource.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of the U.S. Provisional ApplicationNo. 62/103,085 filed on Jan. 14, 2015, which is hereby incorporated byreference as if fully set forth herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a wireless communication system and,more particularly, to a method for transmitting multiplexed HARQfeedbacks in a carrier aggregation system and a device therefor.

2. Discussion of the Related Art

As an example of a mobile communication system to which the presentinvention is applicable, a 3rd Generation Partnership Project Long TermEvolution (hereinafter, referred to as LTE) communication system isdescribed in brief.

FIG. 1 is a view schematically illustrating a network structure of anE-UMTS as an exemplary radio communication system. An Evolved UniversalMobile Telecommunications System (E-UMTS) is an advanced version of aconventional Universal Mobile Telecommunications System (UMTS) and basicstandardization thereof is currently underway in the 3GPP. E-UMTS may begenerally referred to as a Long Term Evolution (LTE) system. For detailsof the technical specifications of the UMTS and E-UMTS, reference can bemade to Release 7 and Release 8 of “3rd Generation Partnership Project;Technical Specification Group Radio Access Network”.

Referring to FIG. 1, the E-UMTS includes a User Equipment (UE), eNode Bs(eNBs), and an Access Gateway (AG) which is located at an end of thenetwork (E-UTRAN) and connected to an external network. The eNBs maysimultaneously transmit multiple data streams for a broadcast service, amulticast service, and/or a unicast service.

One or more cells may exist per eNB. The cell is set to operate in oneof bandwidths such as 1.25, 2.5, 5, 10, 15, and 20 MHz and provides adownlink (DL) or uplink (UL) transmission service to a plurality of UEsin the bandwidth. Different cells may be set to provide differentbandwidths. The eNB controls data transmission or reception to and froma plurality of UEs. The eNB transmits DL scheduling information of DLdata to a corresponding UE so as to inform the UE of a time/frequencydomain in which the DL data is supposed to be transmitted, coding, adata size, and hybrid automatic repeat and request (HARM)-relatedinformation. In addition, the eNB transmits UL scheduling information ofUL data to a corresponding UE so as to inform the UE of a time/frequencydomain which may be used by the UE, coding, a data size, andHARQ-related information. An interface for transmitting user traffic orcontrol traffic may be used between eNBs. A core network (CN) mayinclude the AG and a network node or the like for user registration ofUEs. The AG manages the mobility of a UE on a tracking area (TA) basis.One TA includes a plurality of cells.

Although wireless communication technology has been developed to LTEbased on wideband code division multiple access (WCDMA), the demands andexpectations of users and service providers are on the rise. Inaddition, considering other radio access technologies under development,new technological evolution is required to secure high competitivenessin the future. Decrease in cost per bit, increase in serviceavailability, flexible use of frequency bands, a simplified structure,an open interface, appropriate power consumption of UEs, and the likeare required.

SUMMARY OF THE INVENTION

The object of the present invention can be achieved by providing amethod for a UE operating in a wireless communication system, the methodcomprising: grouping a plurality of cells belonging to an enhanced-NodeB(eNB) to a first Physical Uplink Control Channel (PUCCH) group and asecond PUCCH group, wherein each of the plurality of cells belongs toone of the first PUCCH group and the second PUCCH group; configuring afirst cell with PUCCH resource in the first PUCCH group and a secondcell with PUCCH resource in the second PUCCH group; generating a firstHybrid-ARQ (HARQ) feedback by multiplexing HARQ feedbacks of all HARQprocesses of all cells belonging to the first PUCCH group; generating asecond HARQ feedback by multiplexing HARQ feedbacks of all HARQprocesses of all cells belonging to the second PUCCH group; andtransmitting the first HARQ feedback on the first cell with PUCCHresource and the second HARQ feedback on the second cell with PUCCHresource.

In another aspect of the present invention can be achieved by providinga method for a UE operating in a wireless communication system, themethod comprising: configuring a first cell with Physical Uplink ControlChannel (PUCCH) resource and a second cell with PUCCH resource, whereinthe first cell and the second cell belong to an enhanced-NodeB (eNB);configuring zero or more third cells without PUCCH resource, wherein thezero or more third cells without PUCCH resource are associated with oneof the first cell and the second cell; generating a first HARQ feedbackby multiplexing HARQ feedbacks of all HARQ processes of the first celland third cells associated with the first cell; generating a second HARQfeedback by multiplexing HARQ feedbacks of all HARQ processes of thesecond cell and third cells associated with the second cell; andtransmitting the first HARQ feedback on the first cell with PUCCHresource and the second HARQ feedback on the second cell with PUCCHresource.

Preferably, the first PUCCH group comprises the first cell and zero ormore cells without PUCCH resource, and the second PUCCH group comprisesthe second cell and zero or more cells without PUCCH resource.

Preferably, when the UE configures the first cell, the UE receives anindication indicating which cells of the zero or more third cellswithout PUCCH resource are to be associated with the first cell.

Preferably, when the UE configures the first cell, if the UE doesn'treceive the indication, the first cell is not associated with any of thezero or more third cells.

Preferably, when the UE configures the second cell, the UE receives anindication indicating which cells of the zero or more third cellswithout PUCCH resource are to be associated with the second cell.

Preferably, when the UE configures a third cell among the zero or morethird cells, the UE receives an indication indicating which cell withPUCCH resource is to be associated with the third cell.

Preferably, when the UE configures the third cell among the zero or morethird cells, if the UE doesn't receive the indication, the third cell isassociated with a Primary-Cell (PCell).

Preferably, wherein when the UE multiplexes the HARQ feedbacks of allHARQ processes of all cells belonging to the first PUCCH group, the UEconsiders HARQ feedback of a HARQ process of a cell belonging to thefirst PUCCH Group as ACK (Acknowlegdement) if the HARQ processsuccessfully decodes a received TB (Transport Block), and the UEconsiders HARQ feedback of a HARQ process of a cell belonging to thefirst PUCCH group as NACK (Negative-Acknowledgement) if the HARQ processis allocated to a deactivated cell, or a HARQ process has not receivedany TB, or a HARQ process fails in decoding the received TB, and whenthe UE multiplexes the HARQ feedbacks of all HARQ processes of all cellsbelonging to the second PUCCH group, the UE considers HARQ feedback of aHARQ process of a cell belonging to the second PUCCH group as ACK if theHARQ process successfully decodes a received TB, and the UE considersHARQ feedback of a HARQ process of a cell belonging to the second PUCCHgroup as NACK if the HARQ process is allocated to a deactivated cell, ora HARQ process has not received any TB, or a HARQ process fails indecoding the received TB.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with the description serve to explain the principle of theinvention.

FIG. 1 is a diagram showing a network structure of an Evolved UniversalMobile Telecommunications System (E-UMTS) as an example of a wirelesscommunication system;

FIG. 2A is a block diagram illustrating network structure of an evolveduniversal mobile telecommunication system (E-UMTS), and FIG. 2B is ablock diagram depicting architecture of a typical E-UTRAN and a typicalEPC;

FIG. 3 is a diagram showing a control plane and a user plane of a radiointerface protocol between a UE and an E-UTRAN based on a 3rd generationpartnership project (3GPP) radio access network standard;

FIG. 4 is a diagram of an example physical channel structure used in anE-UMTS system;

FIG. 5 is a block diagram of a communication apparatus according to anembodiment of the present invention;

FIG. 6 is a diagram for carrier aggregation;

FIG. 7 is a conceptual diagram for Dual Connectivity (DC) between aMaster Cell Group (MCS) and a Secondary Cell Group (SCG);

FIG. 8 is a diagram for MAC structure overview in a UE side;

FIG. 9 is a diagram for an activation/deactivation MAC control element;and

FIGS. 10 and 11 are conceptual diagrams for transmitting multiplexedHARQ feedbacks in a carrier aggregation system according to embodimentsof the present invention; and

FIGS. 12A and 12B are examples for transmitting multiplexed HARQfeedbacks in a carrier aggregation system according to embodiments ofthe present invention.

DETAILED DESCRIPTION OF THE INVENTION

Universal mobile telecommunications system (UMTS) is a 3rd Generation(3G) asynchronous mobile communication system operating in wideband codedivision multiple access (WCDMA) based on European systems, globalsystem for mobile communications (GSM) and general packet radio services(GPRS). The long-term evolution (LTE) of UMTS is under discussion by the3rd generation partnership project (3GPP) that standardized UMTS.

The 3GPP LTE is a technology for enabling high-speed packetcommunications. Many schemes have been proposed for the LTE objectiveincluding those that aim to reduce user and provider costs, improveservice quality, and expand and improve coverage and system capacity.The 3G LTE requires reduced cost per bit, increased serviceavailability, flexible use of a frequency band, a simple structure, anopen interface, and adequate power consumption of a terminal as anupper-level requirement.

Hereinafter, structures, operations, and other features of the presentinvention will be readily understood from the embodiments of the presentinvention, examples of which are illustrated in the accompanyingdrawings. Embodiments described later are examples in which technicalfeatures of the present invention are applied to a 3GPP system.

Although the embodiments of the present invention are described using along term evolution (LTE) system and a LTE-advanced (LTE-A) system inthe present specification, they are purely exemplary. Therefore, theembodiments of the present invention are applicable to any othercommunication system corresponding to the above definition. In addition,although the embodiments of the present invention are described based ona frequency division duplex (FDD) scheme in the present specification,the embodiments of the present invention may be easily modified andapplied to a half-duplex FDD (H-FDD) scheme or a time division duplex(TDD) scheme.

FIG. 2A is a block diagram illustrating network structure of an evolveduniversal mobile telecommunication system (E-UMTS). The E-UMTS may bealso referred to as an LTE system. The communication network is widelydeployed to provide a variety of communication services such as voice(VoIP) through IMS and packet data.

As illustrated in FIG. 2A, the E-UMTS network includes an evolved UMTSterrestrial radio access network (E-UTRAN), an Evolved Packet Core (EPC)and one or more user equipment. The E-UTRAN may include one or moreevolved NodeB (eNodeB) 20, and a plurality of user equipment (UE) 10 maybe located in one cell. One or more E-UTRAN mobility management entity(MME)/system architecture evolution (SAE) gateways 30 may be positionedat the end of the network and connected to an external network.

As used herein, “downlink” refers to communication from eNodeB 20 to UE10, and “uplink” refers to communication from the UE to an eNodeB. UE 10refers to communication equipment carried by a user and may be alsoreferred to as a mobile station (MS), a user terminal (UT), a subscriberstation (SS) or a wireless device.

FIG. 2B is a block diagram depicting architecture of a typical E-UTRANand a typical EPC.

As illustrated in FIG. 2B, an eNodeB 20 provides end points of a userplane and a control plane to the UE 10. MME/SAE gateway 30 provides anend point of a session and mobility management function for UE 10. TheeNodeB and MME/SAE gateway may be connected via an S1 interface.

The eNodeB 20 is generally a fixed station that communicates with a UE10, and may also be referred to as a base station (BS) or an accesspoint. One eNodeB 20 may be deployed per cell. An interface fortransmitting user traffic or control traffic may be used between eNodeBs20.

The MME provides various functions including NAS signaling to eNodeBs20, NAS signaling security, AS Security control, Inter CN node signalingfor mobility between 3GPP access networks, Idle mode UE Reachability(including control and execution of paging retransmission), TrackingArea list management (for UE in idle and active mode), PDN GW andServing GW selection, MME selection for handovers with MME change, SGSNselection for handovers to 2G or 3G 3GPP access networks, Roaming,Authentication, Bearer management functions including dedicated bearerestablishment, Support for PWS (which includes ETWS and CMAS) messagetransmission. The SAE gateway host provides assorted functions includingPer-user based packet filtering (by e.g. deep packet inspection), LawfulInterception, UE IP address allocation, Transport level packet markingin the downlink, UL and DL service level charging, gating and rateenforcement, DL rate enforcement based on APN-AMBR. For clarity MME/SAEgateway 30 will be referred to herein simply as a “gateway,” but it isunderstood that this entity includes both an MME and an SAE gateway.

A plurality of nodes may be connected between eNodeB 20 and gateway 30via the S1 interface. The eNodeBs 20 may be connected to each other viaan X2 interface and neighboring eNodeBs may have a meshed networkstructure that has the X2 interface.

As illustrated, eNodeB 20 may perform functions of selection for gateway30, routing toward the gateway during a Radio Resource Control (RRC)activation, scheduling and transmitting of paging messages, schedulingand transmitting of Broadcast Channel (BCCH) information, dynamicallocation of resources to UEs 10 in both uplink and downlink,configuration and provisioning of eNodeB measurements, radio bearercontrol, radio admission control (RAC), and connection mobility controlin LTE ACTIVE state. In the EPC, and as noted above, gateway 30 mayperform functions of paging origination, LTE-IDLE state management,ciphering of the user plane, System Architecture Evolution (SAE) bearercontrol, and ciphering and integrity protection of Non-Access Stratum(NAS) signaling.

The EPC includes a mobility management entity (MME), a serving-gateway(S-GW), and a packet data network-gateway (PDN-GW). The MME hasinformation about connections and capabilities of UEs, mainly for use inmanaging the mobility of the UEs. The S-GW is a gateway having theE-UTRAN as an end point, and the PDN-GW is a gateway having a packetdata network (PDN) as an end point.

FIG. 3 is a diagram showing a control plane and a user plane of a radiointerface protocol between a UE and an E-UTRAN based on a 3GPP radioaccess network standard. The control plane refers to a path used fortransmitting control messages used for managing a call between the UEand the E-UTRAN. The user plane refers to a path used for transmittingdata generated in an application layer, e.g., voice data or Internetpacket data.

A physical (PHY) layer of a first layer provides an information transferservice to a higher layer using a physical channel. The PHY layer isconnected to a medium access control (MAC) layer located on the higherlayer via a transport channel. Data is transported between the MAC layerand the PHY layer via the transport channel. Data is transported betweena physical layer of a transmitting side and a physical layer of areceiving side via physical channels. The physical channels use time andfrequency as radio resources. In detail, the physical channel ismodulated using an orthogonal frequency division multiple access (OFDMA)scheme in downlink and is modulated using a single carrier frequencydivision multiple access (SC-FDMA) scheme in uplink.

The MAC layer of a second layer provides a service to a radio linkcontrol (RLC) layer of a higher layer via a logical channel. The RLClayer of the second layer supports reliable data transmission. Afunction of the RLC layer may be implemented by a functional block ofthe MAC layer. A packet data convergence protocol (PDCP) layer of thesecond layer performs a header compression function to reduceunnecessary control information for efficient transmission of anInternet protocol (IP) packet such as an IP version 4 (IPv4) packet oran IP version 6 (IPv6) packet in a radio interface having a relativelysmall bandwidth.

A radio resource control (RRC) layer located at the bottom of a thirdlayer is defined only in the control plane. The RRC layer controlslogical channels, transport channels, and physical channels in relationto configuration, re-configuration, and release of radio bearers (RBs).An RB refers to a service that the second layer provides for datatransmission between the UE and the E-UTRAN. To this end, the RRC layerof the UE and the RRC layer of the E-UTRAN exchange RRC messages witheach other.

One cell of the eNB is set to operate in one of bandwidths such as 1.25,2.5, 5, 10, 15, and 20 MHz and provides a downlink or uplinktransmission service to a plurality of UEs in the bandwidth. Differentcells may be set to provide different bandwidths.

Downlink transport channels for transmission of data from the E-UTRAN tothe UE include a broadcast channel (BCH) for transmission of systeminformation, a paging channel (PCH) for transmission of paging messages,and a downlink shared channel (SCH) for transmission of user traffic orcontrol messages. Traffic or control messages of a downlink multicast orbroadcast service may be transmitted through the downlink SCH and mayalso be transmitted through a separate downlink multicast channel (MCH).

Uplink transport channels for transmission of data from the UE to theE-UTRAN include a random access channel (RACH) for transmission ofinitial control messages and an uplink SCH for transmission of usertraffic or control messages. Logical channels that are defined above thetransport channels and mapped to the transport channels include abroadcast control channel (BCCH), a paging control channel (PCCH), acommon control channel (CCCH), a multicast control channel (MCCH), and amulticast traffic channel (MTCH).

FIG. 4 is a view showing an example of a physical channel structure usedin an E-UMTS system. A physical channel includes several subframes on atime axis and several subcarriers on a frequency axis. Here, onesubframe includes a plurality of symbols on the time axis. One subframeincludes a plurality of resource blocks and one resource block includesa plurality of symbols and a plurality of subcarriers. In addition, eachsubframe may use certain subcarriers of certain symbols (e.g., a firstsymbol) of a subframe for a physical downlink control channel (PDCCH),that is, an L1/L2 control channel. In FIG. 4, an L1/L2 controlinformation transmission area (PDCCH) and a data area (PDSCH) are shown.In one embodiment, a radio frame of 10 ms is used and one radio frameincludes 10 subframes. In addition, one subframe includes twoconsecutive slots. The length of one slot may be 0.5 ms. In addition,one subframe includes a plurality of OFDM symbols and a portion (e.g., afirst symbol) of the plurality of OFDM symbols may be used fortransmitting the L1/L2 control information. A transmission time interval(TTI) which is a unit time for transmitting data is 1 ms.

A base station and a UE mostly transmit/receive data via a PDSCH, whichis a physical channel, using a DL-SCH which is a transmission channel,except a certain control signal or certain service data. Informationindicating to which UE (one or a plurality of UEs) PDSCH data istransmitted and how the UE receive and decode PDSCH data is transmittedin a state of being included in the PDCCH.

For example, in one embodiment, a certain PDCCH is CRC-masked with aradio network temporary identity (RNTI) “A” and information about datais transmitted using a radio resource “B” (e.g., a frequency location)and transmission format information “C” (e.g., a transmission blocksize, modulation, coding information or the like) via a certainsubframe. Then, one or more UEs located in a cell monitor the PDCCHusing its RNTI information. And, a specific UE with RNTI “A” reads thePDCCH and then receive the PDSCH indicated by B and C in the PDCCHinformation.

FIG. 5 is a block diagram of a communication apparatus according to anembodiment of the present invention.

The apparatus shown in FIG. 5 can be a user equipment (UE) and/or eNBadapted to perform the above mechanism, but it can be any apparatus forperforming the same operation.

As shown in FIG. 5, the apparatus may comprises a DSP/microprocessor(110) and RF module (transmiceiver; 135). The DSP/microprocessor (110)is electrically connected with the transceiver (135) and controls it.The apparatus may further include power management module (105), battery(155), display (115), keypad (120), SIM card (125), memory device (130),speaker (145) and input device (150), based on its implementation anddesigner's choice.

Specifically, FIG. 5 may represent a UE comprising a receiver (135)configured to receive a request message from a network, and atransmitter (135) configured to transmit the transmission or receptiontiming information to the network. These receiver and the transmittercan constitute the transceiver (135). The UE further comprises aprocessor (110) connected to the transceiver (135: receiver andtransmitter).

Also, FIG. 5 may represent a network apparatus comprising a transmitter(135) configured to transmit a request message to a UE and a receiver(135) configured to receive the transmission or reception timinginformation from the UE. These transmitter and receiver may constitutethe transceiver (135). The network further comprises a processor (110)connected to the transmitter and the receiver. This processor (110) maybe configured to calculate latency based on the transmission orreception timing information.

Carrier Aggregation (CA) technology for supporting multiple carriers isdescribed with reference to FIG. 6 as follows. As mentioned in theforegoing description, it may be able to support system bandwidth up tomaximum 100 MHz in a manner of bundling maximum 5 carriers (componentcarriers: CCs) of bandwidth unit (e.g., 20 MHz) defined in a legacywireless communication system (e.g., LTE system) by carrier aggregation.Component carriers used for carrier aggregation may be equal to ordifferent from each other in bandwidth size. And, each of the componentcarriers may have a different frequency band (or center frequency). Thecomponent carriers may exist on contiguous frequency bands. Yet,component carriers existing on non-contiguous frequency bands may beused for carrier aggregation as well. In the carrier aggregationtechnology, bandwidth sizes of uplink and downlink may be allocatedsymmetrically or asymmetrically.

When CA is configured, the UE only has one RRC connection with thenetwork. At RRC connection establishment/re-establishment/handover, oneserving cell provides the NAS mobility information (e.g. TAI), and atRRC connection re-establishment/handover, one serving cell provides thesecurity input. This cell is referred to as the Primary Cell (PCell). Inthe downlink, the carrier corresponding to the PCell is the DownlinkPrimary Component Carrier (DL PCC) while in the uplink it is the UplinkPrimary Component Carrier (UL PCC).

Depending on UE capabilities, Secondary Cells (SCells) can be configuredto form together with the PCell a set of serving cells. In the downlink,the carrier corresponding to an SCell is a Downlink Secondary ComponentCarrier (DL SCC) while in the uplink it is an Uplink Secondary ComponentCarrier (UL SCC).

The primary component carrier is the carrier used by a base station toexchange traffic and control signaling with a user equipment. In thiscase, the control signaling may include addition of component carrier,setting for primary component carrier, uplink (UL) grant, downlink (DL)assignment and the like. Although a base station may be able to use aplurality of component carriers, a user equipment belonging to thecorresponding base station may be set to have one primary componentcarrier only. If a user equipment operates in a single carrier mode, theprimary component carrier is used. Hence, in order to be independentlyused, the primary component carrier should be set to meet allrequirements for the data and control signaling exchange between a basestation and a user equipment.

Meanwhile, the secondary component carrier may include an additionalcomponent carrier that can be activated or deactivated in accordancewith a required size of transceived data. The secondary componentcarrier may be set to be used only in accordance with a specific commandand rule received from a base station. In order to support an additionalbandwidth, the secondary component carrier may be set to be usedtogether with the primary component carrier. Through an activatedcomponent carrier, such a control signal as a UL grant, a DL assignmentand the like can be received by a user equipment from a base station.Through an activated component carrier, such a control signal in UL as achannel quality indicator (CQI), a precoding matrix index (PMI), a rankindicator (RI), a sounding reference signal (SRS) and the like can betransmitted to a base station from a user equipment.

Resource allocation to a user equipment can have a range of a primarycomponent carrier and a plurality of secondary component carriers. In amulti-carrier aggregation mode, based on a system load (i.e.,static/dynamic load balancing), a peak data rate or a service qualityrequirement, a system may be able to allocate secondary componentcarriers to DL and/or UL asymmetrically. In using the carrieraggregation technology, the setting of the component carriers may beprovided to a user equipment by a base station after RRC connectionprocedure. In this case, the RRC connection may mean that a radioresource is allocated to a user equipment based on RRC signalingexchanged between an RRC layer of the user equipment and a network viaSRB. After completion of the RRC connection procedure between the userequipment and the base station, the user equipment may be provided bythe base station with the setting information on the primary componentcarrier and the secondary component carrier. The setting information onthe secondary component carrier may include addition/deletion (oractivation/deactivation) of the secondary component carrier. Therefore,in order to activate a secondary component carrier between a basestation and a user equipment or deactivate a previous secondarycomponent carrier, it may be necessary to perform an exchange of RRCsignaling and MAC control element.

The configured set of serving cells for a UE therefore always consistsof one PCell and one or more SCells:

-   -   For each SCell the usage of uplink resources by the UE in        addition to the downlink ones is configurable (the number of DL        SCCs configured is therefore always larger than or equal to the        number of UL SCCs and no SCell can be configured for usage of        uplink resources only);    -   From a UE viewpoint, each uplink resource only belongs to one        serving cell;    -   The number of serving cells that can be configured depends on        the aggregation capability of the UE;    -   PCell can only be changed with handover procedure (i.e. with        security key change and RACH procedure);    -   PCell is used for transmission of PUCCH;    -   Unlike SCells, PCell cannot be de-activated;    -   Re-establishment is triggered when PCell experiences RLF, not        when SCells experience RLF;    -   NAS information is taken from PCell.

The activation or deactivation of the secondary component carrier may bedetermined by a base station based on a quality of service (QoS), a loadcondition of carrier and other factors. And, the base station may beable to instruct a user equipment of secondary component carrier settingusing a control message including such information as an indication type(activation/deactivation) for DL/UL, a secondary component carrier listand the like.

The reconfiguration, addition and removal of SCells can be performed byRRC. At intra-LTE handover, RRC can also add, remove, or reconfigureSCells for usage with the target PCell. When adding a new SCell,dedicated RRC signalling is used for sending all required systeminformation of the SCell i.e. while in connected mode, UEs need notacquire broadcasted system information directly from the SCells.

FIG. 7 is a conceptual diagram for Dual Connectivity (DC) between aMaster Cell Group (MCS) and a Secondary Cell Group (SCG).

The Dual Connectivity (DC) means that the UE can be connected to both aMaster eNode-B (MeNB) and a Secondary eNode-B (SeNB) at the same time.The MCG is a group of serving cells associated with the MeNB, comprisingof a PCell and optionally one or more SCells. And the SCG is a group ofserving cells associated with the SeNB, comprising of the special SCelland optionally one or more SCells. The MeNB is an eNB which terminatesat least S1-MME (S1 for the control plane) and the SeNB is an eNB thatis providing additional radio resources for the UE but is not the MeNB.

The Dual Connectivity is a kind of carrier aggregation in that the UE isconfigured a plurality serving cells. However, unlike all serving cellssupporting carrier aggregation of FIG. 6 are served by a same eNB, allserving cells supporting dual connectivity of FIG. 7 are served bydifferent eNBs, respectively at same time. The different eNBs areconnected via non-ideal backhaul interface because the UE is connectedwith the different eNBs at same time.

With Dual Connectivity, some of the data radio bearers (DRBs) can beoffloaded to the SCG to provide high throughput while keeping schedulingradio bearers (SRBs) or other DRBs in the MCG to reduce the handoverpossibility. The MCG is operated by the MeNB via the frequency of f1,and the SCG is operated by the SeNB via the frequency of f2. Thefrequency f1 and f2 may be equal. The backhaul interface (BH) betweenthe MeNB and the SeNB is non-ideal (e.g. X2 interface), which means thatthere is considerable delay in the backhaul and therefore thecentralized scheduling in one node is not possible.

For SCG, the following principles are applied:

-   -   At least one cell in SCG has a configured UL CC and one of them,        named PSCell, is configured with PUCCH resources;    -   When SCG is configured, there is always at least one SCG bearer        or one Split bearer;    -   Upon detection of a physical layer problem or a random access        problem on PSCell, or the maximum number of RLC retransmissions        has been reached associated with the SCG, or upon detection of        an access problem on PSCell (T307 expiry) during SCG addition or        SCG change:    -   RRC connection Re-establishment procedure is not triggered;    -   All UL transmissions towards all cells of the SCG are stopped;    -   MeNB is informed by the UE of SCG failure type.    -   For split bearer, the DL data transfer over the MeNB is        maintained.    -   Only the RLC AM bearer can be configured for the split bearer;    -   Like PCell, PSCell cannot be de-activated;    -   PSCell can only be changed with SCG change (i.e. with security        key change and RACH procedure);    -   Neither direct bearer type change between Split bearer and SCG        bearer nor simultaneous configuration of SCG and Split bearer        are supported.

With respect to the interaction between MeNB and SeNB, the followingprinciples are applied:

-   -   The MeNB maintains the RRM measurement configuration of the UE        and may, e.g, based on received measurement reports or traffic        conditions or bearer types, decide to ask a SeNB to provide        additional resources (serving cells) for a UE.    -   Upon receiving the request from the MeNB, a SeNB may create the        container that will result in the configuration of additional        serving cells for the UE (or decide that it has no resource        available to do so).    -   For UE capability coordination, the MeNB provides (part of) the        AS configuration and the UE capabilities to the SeNB.    -   The MeNB and the SeNB exchange information about UE        configuration by means of RRC containers (inter-node messages)        carried in X2 messages.    -   The SeNB may initiate a reconfiguration of its existing serving        cells (e.g., PUCCH towards the SeNB).    -   The SeNB decides which cell is the PSCell within the SCG.    -   The MeNB does not change the content of the RRC configuration        provided by the SeNB.    -   In the case of the SCG addition and SCG SCell addition, the MeNB        may provide the latest measurement results for the SCG cell(s).    -   Both MeNB and SeNB know the SFN and subframe offset of each        other by OAM, e.g., for the purpose of DRX alignment and        identification of measurement gap.

When adding a new SCG SCell, dedicated RRC signalling is used forsending all required system information of the cell as for CA describedabove, except for the SFN acquired from MIB of the PSCell of SCG.

FIG. 8 is a diagram for MAC structure overview in a UE side.

The MAC layer handles logical-channel multiplexing, hybrid-ARQretransmissions, and uplink and downlink scheduling. It is alsoresponsible for multiplexing/demultiplexing data across multiplecomponent carriers when carrier aggregation is used.

The MAC provides services to the RLC in the form of logical channels. Alogical channel is defined by the type of information it carries and isgenerally classified as a control channel, used for transmission ofcontrol and configuration information necessary for operating an LTEsystem, or as a traffic channel, used for the user data. The set oflogical-channel types specified for LTE includes:

-   -   The Broadcast Control Channel (BCCH), used for transmission of        system information from the network to all terminals in a cell.        Prior to accessing the system, a terminal needs to acquire the        system information to find out how the system is configured and,        in general, how to behave properly within a cell.    -   The Paging Control Channel (PCCH), used for paging of terminals        whose location on a cell level is not known to the network. The        paging message therefore needs to be transmitted in multiple        cells.    -   The Common Control Channel (CCCH), used for transmission of        control information in conjunction with random access.    -   The Dedicated Control Channel (DCCH), used for transmission of        control information to/from a terminal. This channel is used for        individual configuration of terminals such as different handover        messages.    -   The Multicast Control Channel (MCCH), used for transmission of        control information required for reception of the MTCH.    -   The Dedicated Traffic Channel (DTCH), used for transmission of        user data to/from a terminal. This is the logical channel type        used for transmission of all uplink and non-MBSFN downlink user        data.    -   The Multicast Traffic Channel (MTCH), used for downlink        transmission of MBMS services.

From the physical layer, the MAC layer uses services in the form oftransport channels. A transport channel is defined by how and with whatcharacteristics the information is transmitted over the radio interface.Data on a transport channel is organized into transport blocks. In eachTransmission Time Interval (TTI), at most one transport block of dynamicsize is transmitted over the radio interface to/from a terminal in theabsence of spatial multiplexing. In the case of spatial multiplexing(MIMO), there can be up to two transport blocks per TTI.

Associated with each transport block is a Transport Format (TF),specifying how the transport block is to be transmitted over the radiointerface. The transport format includes information about thetransport-block size, the modulation-and-coding scheme, and the antennamapping. By varying the transport format, the MAC layer can thus realizedifferent data rates. Rate control is therefore also known astransport-format selection.

The following transport-channel types are defined for LTE:

-   -   The Broadcast Channel (BCH) has a fixed transport format,        provided by the specifications. It is used for transmission of        parts of the BCCH system information, more specifically the        so-called Master Information Block (MIB).    -   The Paging Channel (PCH) is used for transmission of paging        information from the PCCH logical channel. The PCH supports        discontinuous reception (DRX) to allow the terminal to save        battery power by waking up to receive the PCH only at predefined        time instants. The Downlink Shared Channel (DL-SCH) is the main        transport channel used for transmission of downlink data in LTE.        It supports key LTE features such as dynamic rate adaptation and        channel-dependent scheduling in the time and frequency domains,        hybrid ARQ with soft combining, and spatial multiplexing. It        also supports DRX to reduce terminal power consumption while        still providing an always-on experience. The DL-SCH is also used        for transmission of the parts of the BCCH system information not        mapped to the BCH. There can be multiple DL-SCHs in a cell, one        per terminal scheduled in this TTI, and, in some subframes, one        DL-SCH carrying system information.    -   The Multicast Channel (MCH) is used to support MBMS. It is        characterized by a semi-static transport format and semi-static        scheduling. In the case of multi-cell transmission using MBSFN,        the scheduling and transport format configuration is coordinated        among the transmission points involved in the MBSFN        transmission.    -   The Uplink Shared Channel (UL-SCH) is the uplink counterpart to        the DL-SCH—that is, the uplink transport channel used for        transmission of uplink data.

In addition, the Random-Access Channel (RACH) is also defined as atransport channel, although it does not carry transport blocks.

To support priority handling, multiple logical channels, where eachlogical channel has its own RLC entity, can be multiplexed into onetransport channel by the MAC layer. At the receiver, the MAC layerhandles the corresponding demultiplexing and forwards the RLC PDUs totheir respective RLC entity for in-sequence delivery and the otherfunctions handled by the RLC. To support the demultiplexing at thereceiver, a MAC is used. To each RLC PDU, there is an associatedsub-header in the MAC header. The sub-header contains the identity ofthe logical channel (LCID) from which the RLC PDU originated and thelength of the PDU in bytes. There is also a flag indicating whether thisis the last sub-header or not. One or several RLC PDUs, together withthe MAC header and, if necessary, padding to meet the scheduledtransport-block size, form one transport block which is forwarded to thephysical layer.

In addition to multiplexing of different logical channels, the MAC layercan also insert the so-called MAC control elements into the transportblocks to be transmitted over the transport channels. A MAC controlelement is used for inband control signaling—for example, timing-advancecommands and random-access response. Control elements are identifiedwith reserved values in the LCID field, where the LCID value indicatesthe type of control information.

Furthermore, the length field in the sub-header is removed for controlelements with a fixed length.

The MAC multiplexing functionality is also responsible for handling ofmultiple component carriers in the case of carrier aggregation. Thebasic principle for carrier aggregation is independent processing of thecomponent carriers in the physical layer, including control signaling,scheduling and hybrid-ARQ retransmissions, while carrier aggregation isinvisible to RLC and PDCP. Carrier aggregation is therefore mainly seenin the MAC layer, where logical channels, including any MAC controlelements, are multiplexed to form one (two in the case of spatialmultiplexing) transport block(s) per component carrier with eachcomponent carrier having its own hybrid-ARQ entity.

In Dual Connectivity, two MAC entities are configured in the UE: one forthe MCG and one for the SCG. Each MAC entity is configured by RRC with aserving cell supporting PUCCH transmission and contention based RandomAccess. In this specification, the term SpCell refers to such cell,whereas the term SCell refers to other serving cells. The term SpCelleither refers to the PCell of the MCG or the PSCell of the SCG dependingon if the MAC entity is associated to the MCG or the SCG, respectively.A Timing Advance Group containing the SpCell of a MAC entity is referredto as pTAG, whereas the term sTAG refers to other TAGs.

If a reset of the MAC entity is requested by upper layers, the MACentity shall:

-   -   initialize Bj for each logical channel to zero;    -   stop (if running) all timers;    -   consider all timeAlignmentTimers as expired;    -   set the NDIs for all uplink HARQ processes to the value 0;    -   stop, if any, ongoing RACH procedure;    -   discard explicitly signalled ra-PreambleIndex and        ra-PRACH-MaskIndex, if any;    -   flush Msg3 buffer;    -   cancel, if any, triggered Scheduling Request procedure;    -   cancel, if any, triggered Buffer Status Reporting procedure;    -   cancel, if any, triggered Power Headroom Reporting procedure;    -   flush the soft buffers for all DL HARQ processes;    -   for each DL HARQ process, consider the next received        transmission for a TB as the very first transmission;    -   release, if any, Temporary C-RNTI.

FIG. 9 is a diagram for an activation/deactivation MAC control element.

If the UE is configured with one or more SCells, the network mayactivate and deactivate the configured SCells. The PCell is alwaysactivated. The network activates and deactivates the SCell(s) by sendingthe Activation/Deactivation MAC control element. Furthermore, the UEmaintains a sCellDeactivationTimer timer per configured SCell anddeactivates the associated SCell upon its expiry. The same initial timervalue applies to each instance of the sCellDeactivationTimer and it isconfigured by RRC. The configured SCells are initially deactivated uponaddition and after a handover.

The UE configures each SCell to each TTI and for each configured SCell:

If the UE receives an Activation/Deactivation MAC control element inthis TTI activating the SCell, the UE may activate the SCell in the TTI.The UE can apply normal SCell operation including i) SRS transmissionson the SCell, ii) CQI/PMI/RI/PTI reporting for the SCell, iii) PDCCHmonitoring on the SCell, or iv) PDCCH monitoring for the SCell. Also theUE may start or restart the sCellDeactivationTimer associated with theSCell and trigger PHR.

If the UE receives an Activation/Deactivation MAC control element inthis TTI deactivating the SCell, or if the sCellDeactivationTimerassociated with the activated SCell expires in this TTI, the UE candeactivate the SCell in the TTI, stop the sCellDeactivationTimerassociated with the SCell, and flush all HARQ buffers associated withthe SCell.

If PDCCH on the activated SCell indicates an uplink grant or downlinkassignment; or if PDCCH on the Serving Cell scheduling the activatedSCell indicates an uplink grant or a downlink assignment for theactivated SCell, the UE can restart the sCellDeactivationTimerassociated with the SCell.

If the SCell is deactivated, the UE will not transmit SRS on the SCell,transmit on UL-SCH on the SCell, transmit on RACH on the SCell, monitorthe PDCCH on the SCell, or monitor the PDCCH for the SCell.

HARQ feedback for the MAC PDU containing Activation/Deactivation MACcontrol element may not be impacted by PCell interruption due to SCellactivation/deactivation.

The Activation/Deactivation MAC control element is identified by a MACPDU subheader with LCID as specified in table 1. It has a fixed size andconsists of a single octet containing seven C-fields and one R-field.The Activation/Deactivation MAC control element is defined as FIG. 9

TABLE 1 Index LCID values 00000 CCCH 00001-01010 Identity of the logicalchannel 01011-11001 Reserved 11010 Long DRX Command 11011Activation/Deactivation 11100 UE Contention Resolution Identity 11101Timing Advance Command 11110 DRX Command 11111 Padding

Ci field indicates the activation/deactivation status of the SCell withSCellIndex i, if there is an SCell configured with SCellIndex i. Else,the UE may ignore the Ci field. The Ci field is set to “1” to indicatethat the SCell with SCellIndex i shall be activated. The Ci field is setto “0” to indicate that the SCell with SCellIndex i shall bedeactivated. R field is a reserved bit, and set to ‘0’.

The sCellDeactivationTimer is a SCell deactivation timer. Value innumber of radio frames. Value rf4 corresponds to 4 radio frames, valuerf8 corresponds to 8 radio frames and so on. E-UTRAN only configures thefield if the UE is configured with one or more SCells other than thePSCell. If the field is absent, the UE shall delete any existing valuefor this field and assume the value to be set to infinity. The samevalue applies for each SCell of a Cell Group (i.e. MCG or SCG) (althoughthe associated functionality is performed independently for each SCell).

Up to Rel-12, only one cell in a Cell Group can be configured with PUCCHresource, i.e., the special cell in CA/DC, which is always activated. InRel-13, cells other the special cell could be configured with PUCCHresource in order to offload the PUCCH traffic from the special cell toother cells.

In the legacy, as there is one cell configured with PUCCH resource,there is only one PUCCH resource in a given TTI and the UE transmitsHARQ feedback on that PUCCH resource by gathering ACK and NACK feedbacksof all configured cells. Note that for the cell in Deactivated state,the UE considers the feedback as NACK.

In Rel-13, if the network wants to configure multiple PUCCH resourcesfor a UE, a new mechanism is required in consideration of the followingaspects: i) How to configure multiple PUCCH resources for a UE, ii) Howto multiplex HARQ feedbacks of the cells configured for the UE, and iii)How to transmit the HARQ feedback to the network.

FIG. 10 is a conceptual diagram for transmitting multiplexed HARQfeedbacks in a carrier aggregation system according to embodiments ofthe present invention.

In this invention, a UE is configured with one PUCCH cell per PUCCHGroup, generates a multiplexed HARQ feedback by multiplexing HARQfeedbacks of all HARQ processes of all configured cells belonging to thePUCCH Group, and transmits the multiplexed HARQ feedback on the PUCCHcell of the PUCCH Group. For this, the PUCCH Group includes one PUCCHcell and zero or more non-PUCCH cell.

In this manner, PUCCH cell refers to a cell configured with PUCCHresource and non-PUCCH cell refers to a cell not configured with PUCCHresource.

The UE groups a plurality of cells belonging to an enhanced-NodeB (eNB)to a first Physical Uplink Control Channel (PUCCH) group and a secondPUCCH group, wherein each of the plurality of cells belongs to one ofthe first PUCCH group and the second PUCCH group (S1001). And in thiscase the UE configures a first cell with PUCCH resource in the firstPUCCH group and a second cell with PUCCH resource in the second PUCCHgroup (S1003).

Preferably, the first PUCCH group comprises the first cell and zero ormore cells without PUCCH resource, and the second PUCCH group comprisesthe second cell and zero or more cells without PUCCH resource.

In other word, the first cell with PUCCH resource is associated withzero or more cells without PUCCH resource in the first PUCCH group, andthe second cell with PUCCH resource is associated with zero or morecells without PUCCH resource in the second PUCCH group. When it is saidthat ‘a non-PUCCH cell is associated with (or mapped to) a PUCCH cell’,it means that HARQ feedback of the non-PUCCH cell is to be transmittedon the PUCCH cell.

In a TTI where the HARQ feedback needs to be transmitted for at leastone HARQ process of a cell, the UE generates a first Hybrid-ARQ (HARQ)feedback by multiplexing HARQ feedbacks of all HARQ processes of allcells belonging to the first PUCCH group, and generates a second HARQfeedback by multiplexing HARQ feedbacks of all HARQ processes of allcells belonging to the second PUCCH group (S1005).

Preferably, only the HARQ process that successfully decodes the receivedTB generates HARQ feedback as ACK. And all other HARQ processes generateHARQ feedback as NACK. For example, if the HARQ process allocated to thedeactivated cell, or if the HARQ process that has not received any TB,or the HARQ process that fails in decoding received TB, the UE considersthe HARQ feedback as NACK.

In other word, when the UE multiplexes the HARQ feedbacks of all HARQprocesses of all cells belonging to the first PUCCH group, the UEconsiders HARQ feedback of a HARQ process of a cell belonging to thefirst PUCCH Group as ACK (Acknowlegdement) if the HARQ processsuccessfully decodes a received TB (Transport Block), and the UEconsiders HARQ feedback of a HARQ process of a cell belonging to thefirst PUCCH group as NACK (Negative-Acknowledgement) if the HARQ processis allocated to a deactivated cell, or a HARQ process has not receivedany TB, or a HARQ process fails in decoding the received TB, and whenthe UE multiplexes the HARQ feedbacks of all HARQ processes of all cellsbelonging to the second PUCCH group, the UE considers HARQ feedback of aHARQ process of a cell belonging to the second PUCCH group as ACK if theHARQ process successfully decodes a received TB, and the UE considersHARQ feedback of a HARQ process of a cell belonging to the second PUCCHgroup as NACK if the HARQ process is allocated to a deactivated cell, ora HARQ process has not received any TB, or a HARQ process fails indecoding the received TB.

And the UE then transmits the first HARQ feedback on the first cell withPUCCH resource and the second HARQ feedback on the second cell withPUCCH resource (S1007).

FIG. 11 is a conceptual diagram for transmitting multiplexed HARQfeedbacks in a carrier aggregation system according to embodiments ofthe present invention.

The UE configure a first cell with PUCCH resource and a second cell withPUCCH resource, wherein the first cell and the second cell belong to aneNB (S1101). And the UE configures zero or more third cells withoutPUCCH resource, wherein the zero or more third cells without PUCCHresource are associated with one of the first cell and the second cell(S1103).

In this manner, PUCCH cell refers to a cell configured with PUCCHresource and non-PUCCH cell refers to a cell not configured with PUCCHresource. Thus, the first cell and the second cell are PUCCH cell andthe zero or more third cells are non-PUCCH cells.

When it is said that ‘a non-PUCCH cell is associated with (or mapped to)a PUCCH cell’, it means that HARQ feedback of the non-PUCCH cell is tobe transmitted on the PUCCH cell.

When the UE configures the first cell, the UE receives an indicationindicating which cells of the zero or more third cells without PUCCHresource are to be associated with the first cell. And when the UEconfigures the second cell also, the UE receives an indicationindicating which cells of the zero or more third cells without PUCCHresource are to be associated with the second cell.

Preferably, the indication includes PUCCH resource or an indication ofnon-PUCCH cells mapped to the PUCCH cell.

When the UE receives the control signaling that configures a PUCCH cell,the UE shall consider that the PUCCH cell and the non-PUCCH cellsindicated by the control signaling belong to the PUCCH group that usesthe PUCCH cell.

Meanwhile, when the UE configures the first cell, if the UE doesn'treceive the indication, the first cell is not associated with any of thezero or more third cells.

When the UE configures a third cell among the zero or more third cells,the UE receives an indication indicating which cell with PUCCH resourceis to be associated with the third cell.

Preferably, the indication includes PUCCH resource or an indication of aPUCCH cell on which the HARQ feedback of the HARQ processes of thenon-PUCCH cell is transmitted.

When the UE receives the control signaling that configures a non-PUCCHcell, the UE shall consider that the non-PUCCH cell belongs to the PUCCHgroup that uses the PUCCH cell indicated by the control signaling.

When the UE configures the third cell among the zero or more thirdcells, if the UE doesn't receive the indication, the UE shall considerthat the non-PUCCH cell belongs to a default PUCCH group, e.g. PUCCHgroup that uses PCell or PSCell. That means the third cell is associatedwith a Primary-Cell (PCell).

The UE generates a first HARQ feedback by multiplexing HARQ feedbacks ofall HARQ processes of the first cell and third cells associated with thefirst cell, and generates a second HARQ feedback by multiplexing HARQfeedbacks of all HARQ processes of the second cell and third cellsassociated with the second cell (S1105).

In this case, when the UE multiplexes the HARQ feedbacks of all HARQprocesses of all cells belonging to the first PUCCH group, the UEconsiders HARQ feedback of a HARQ process of a cell belonging to thefirst PUCCH Group as ACK (Acknowlegdement) if the HARQ processsuccessfully decodes a received TB (Transport Block), and the UEconsiders HARQ feedback of a HARQ process of a cell belonging to thefirst PUCCH group as NACK (Negative-Acknowledgement) if the HARQ processis allocated to a deactivated cell, or a HARQ process has not receivedany TB, or a HARQ process fails in decoding the received TB, and whenthe UE multiplexes the HARQ feedbacks of all HARQ processes of all cellsbelonging to the second PUCCH group, the UE considers HARQ feedback of aHARQ process of a cell belonging to the second PUCCH group as ACK if theHARQ process successfully decodes a received TB, and the UE considersHARQ feedback of a HARQ process of a cell belonging to the second PUCCHgroup as NACK if the HARQ process is allocated to a deactivated cell, ora HARQ process has not received any TB, or a HARQ process fails indecoding the received TB.

And the UE then transmits the first HARQ feedback on the first cell withPUCCH resource and the second HARQ feedback on the second cell withPUCCH resource (S1107).

FIGS. 12A and 12B are examples for transmitting multiplexed HARQfeedbacks in a carrier aggregation system according to embodiments ofthe present invention.

FIG. 12A is an example for one PUCCH configuration per Group.

The eNB configures multiple PUCCH cells for a UE by grouping the cells.In a group (hereafter, it is PUCCH Group), there is only one PUCCH celland the UE transmits the HARQ feedbacks of all cells within the PUCCHGroup via the PUCCH cell. UE possibly performs multiple PUCCHtransmissions at one point in time.

In case of FIG. 12A, RAN2 need to discuss how to indicate the PUCCHGroup and the cells belonging to the PUCCH Group, how to modify thePUCCH Group (removal/change of PUCCH Cell), etc. From UE point of view,as there can be multiple PUCCH Groups, multiple PUCCH transmission mayoccur at the same time. Depending on the number of PUCCH Groups, RAN2may need to discuss how to support PUCCH transmissions on multiple cellsin consideration of e.g., power limitation.

FIG. 12B is an example for Multiple PUCCH configuration per UE.

The eNB configures multiple PUCCH cells for a UE. The UE transmits theHARQ feedbacks of all cells via one of the PUCCH cells at one point intime.

As there can be multiple PUCCH cells, the PUCCH Cell which is to be usedfor HARQ feedback transmission at one point in time can be decided byeither the eNB or the UE based on a certain criterion.

In our understanding, both models would achieve PUCCH offloading byconfiguring multiple PUCCH cells for a UE. However, model 1 (case ofFIG. 12a ) requires more standardization efforts on procedure/signallingdesign in order to support removal/change of PUCCH cell of PUCCH groupand addition/removal/change of the PUCCH Group. In addition, model 1increases the UE complexity in order to support simultaneous PUCCHtransmissions on multiple PUCCH Cells with the limited UE power. Giventhat model 1 would apply to each Cell Group in DC, the number ofsimultaneous PUCCH transmissions would increase in DC. Then, a carefulconsideration is required to ensure the successful PUCCH transmissionwith the limited UE power. On the other hand, in model 2 (case of FIG.12b ), removal/change of PUCCH Cell would be simpler than that in model1 because at least one cell, i.e., PCell, is always configured withPUCCH for all cells. Therefore, model 2 seems to provide more flexibleand dynamic PUCCH offloading.

The embodiments of the present invention described hereinbelow arecombinations of elements and features of the present invention. Theelements or features may be considered selective unless otherwisementioned. Each element or feature may be practiced without beingcombined with other elements or features. Further, an embodiment of thepresent invention may be constructed by combining parts of the elementsand/or features. Operation orders described in embodiments of thepresent invention may be rearranged. Some constructions of any oneembodiment may be included in another embodiment and may be replacedwith corresponding constructions of another embodiment. It is obvious tothose skilled in the art that claims that are not explicitly cited ineach other in the appended claims may be presented in combination as anembodiment of the present invention or included as a new claim bysubsequent amendment after the application is filed.

In the embodiments of the present invention, a specific operationdescribed as performed by the BS may be performed by an upper node ofthe BS. Namely, it is apparent that, in a network comprised of aplurality of network nodes including a BS, various operations performedfor communication with an MS may be performed by the BS, or networknodes other than the BS. The term eNB′ may be replaced with the term‘fixed station’, ‘Node B’, ‘Base Station (BS)’, ‘access point’, etc.

The above-described embodiments may be implemented by various means, forexample, by hardware, firmware, software, or a combination thereof.

In a hardware configuration, the method according to the embodiments ofthe present invention may be implemented by one or more ApplicationSpecific Integrated Circuits (ASICs), Digital Signal Processors (DSPs),Digital Signal Processing Devices (DSPDs), Programmable Logic Devices(PLDs), Field Programmable Gate Arrays (FPGAs), processors, controllers,microcontrollers, or microprocessors.

In a firmware or software configuration, the method according to theembodiments of the present invention may be implemented in the form ofmodules, procedures, functions, etc. performing the above-describedfunctions or operations. Software code may be stored in a memory unitand executed by a processor. The memory unit may be located at theinterior or exterior of the processor and may transmit and receive datato and from the processor via various known means.

Those skilled in the art will appreciate that the present invention maybe carried out in other specific ways than those set forth hereinwithout departing from the spirit and essential characteristics of thepresent invention. The above embodiments are therefore to be construedin all aspects as illustrative and not restrictive. The scope of theinvention should be determined by the appended claims and their legalequivalents, not by the above description, and all changes coming withinthe meaning and equivalency range of the appended claims are intended tobe embraced therein.

What is claimed is:
 1. A method for a User Equipment (UE) operating in awireless communication system, the method comprising: grouping aplurality of cells belonging to an enhanced-NodeB (eNB) to a firstPhysical Uplink Control Channel (PUCCH) group and a second PUCCH group,wherein each of the plurality of cells belongs to one of the first PUCCHgroup and the second PUCCH group; configuring a first cell with PUCCHresource in the first PUCCH group and a second cell with PUCCH resourcein the second PUCCH group; generating a first Hybrid-ARQ (HARQ) feedbackby multiplexing HARQ feedbacks of all HARQ processes of all cellsbelonging to the first PUCCH group; generating a second HARQ feedback bymultiplexing HARQ feedbacks of all HARQ processes of all cells belongingto the second PUCCH group; and transmitting the first HARQ feedback onthe first cell with PUCCH resource and the second HARQ feedback on thesecond cell with PUCCH resource.
 2. The method according to claim 1,wherein the first PUCCH group comprises the first cell and zero or morecells without PUCCH resource, and the second PUCCH group comprises thesecond cell and zero or more cells without PUCCH resource.
 3. The methodaccording to claim 1, wherein when the UE multiplexes the HARQ feedbacksof all HARQ processes of all cells belonging to the first PUCCH group,the UE considers HARQ feedback of a HARQ process of a cell belonging tothe first PUCCH Group as ACK (Acknowlegdement) if the HARQ processsuccessfully decodes a received TB (Transport Block), and the UEconsiders HARQ feedback of a HARQ process of a cell belonging to thefirst PUCCH group as NACK (Negative-Acknowledgement) if the HARQ processis allocated to a deactivated cell, or a HARQ process has not receivedany TB, or a HARQ process fails in decoding the received TB, and whenthe UE multiplexes the HARQ feedbacks of all HARQ processes of all cellsbelonging to the second PUCCH group, the UE considers HARQ feedback of aHARQ process of a cell belonging to the second PUCCH group as ACK if theHARQ process successfully decodes a received TB, and the UE considersHARQ feedback of a HARQ process of a cell belonging to the second PUCCHgroup as NACK if the HARQ process is allocated to a deactivated cell, ora HARQ process has not received any TB, or a HARQ process fails indecoding the received TB.
 4. A method for a User Equipment (UE)operating in a wireless communication system, the method comprising:configuring a first cell with Physical Uplink Control Channel (PUCCH)resource and a second cell with PUCCH resource, wherein the first celland the second cell belong to an enhanced-NodeB (eNB); configuring zeroor more third cells without PUCCH resource, wherein the zero or morethird cells without PUCCH resource are associated with one of the firstcell and the second cell; generating a first HARQ feedback bymultiplexing HARQ feedbacks of all HARQ processes of the first cell andthird cells associated with the first cell; generating a second HARQfeedback by multiplexing HARQ feedbacks of all HARQ processes of thesecond cell and third cells associated with the second cell; andtransmitting the first HARQ feedback on the first cell with PUCCHresource and the second HARQ feedback on the second cell with PUCCHresource.
 5. The method according to claim 4, wherein when the UEconfigures the first cell, the UE receives an indication indicatingwhich cells of the zero or more third cells without PUCCH resource areto be associated with the first cell.
 6. The method according to claim5, wherein when the UE configures the first cell, if the UE doesn'treceive the indication, the first cell is not associated with any of thezero or more third cells.
 7. The method according to claim 4, whereinwhen the UE configures the second cell, the UE receives an indicationindicating which cells of the zero or more third cells without PUCCHresource are to be associated with the second cell.
 8. The methodaccording to claim 4, wherein when the UE configures a third cell amongthe zero or more third cells, the UE receives an indication indicatingwhich cell with PUCCH resource is to be associated with the third cell.9. The method according to claim 8, wherein when the UE configures thethird cell among the zero or more third cells, if the UE doesn't receivethe indication, the third cell is associated with a Primary-Cell(PCell).
 10. The method according to claim 4, wherein when the UEmultiplexes the HARQ feedbacks of all HARQ processes of all cellsbelonging to the first PUCCH group, the UE considers HARQ feedback of aHARQ process of a cell belonging to the first PUCCH Group as ACK(Acknowlegdement) if the HARQ process successfully decodes a received TB(Transport Block), and the UE considers HARQ feedback of a HARQ processof a cell belonging to the first PUCCH group as NACK(Negative-Acknowledgement) if the HARQ process is allocated to adeactivated cell, or a HARQ process has not received any TB, or a HARQprocess fails in decoding the received TB, and when the UE multiplexesthe HARQ feedbacks of all HARQ processes of all cells belonging to thesecond PUCCH group, the UE considers HARQ feedback of a HARQ process ofa cell belonging to the second PUCCH group as ACK if the HARQ processsuccessfully decodes a received TB, and the UE considers HARQ feedbackof a HARQ process of a cell belonging to the second PUCCH group as NACKif the HARQ process is allocated to a deactivated cell, or a HARQprocess has not received any TB, or a HARQ process fails in decoding thereceived TB.
 11. A User Equipment (UE) operating in a wirelesscommunication system, the UE comprising: a Radio Frequency (RF) module;and a processor configured to control the RF module, wherein theprocessor is configured to group a plurality of cells to a firstPhysical Uplink Control Channel (PUCCH) group and a second PUCCH group,wherein the plurality of cells belong to an enhanced-NodeB (eNB), toconfigure a first cell with PUCCH resource in the first PUCCH group anda second cell with PUCCH resource in the second PUCCH group, to generatea first Hybrid-ARQ (HARQ) feedback by multiplexing HARQ feedbacks of allHARQ processes of all cells belonging to the first PUCCH group, togenerate a second HARQ feedback by multiplexing HARQ feedbacks of allHARQ processes of all cells belonging to the second PUCCH group, and totransmit the first HARQ feedback on the first cell with PUCCH resourceand the second HARQ feedback on the second cell with PUCCH resource. 12.The UE according to claim 11, wherein the first PUCCH group comprisesthe first cell and zero or more cells without PUCCH resource, and thesecond PUCCH group comprises the second cell and zero or more cellswithout PUCCH resource.
 13. The UE according to claim 11, wherein whenthe processor generates the first HARQ feedback, only if a HARQ processsuccessfully decodes a received TB, the UE considers the first HARQfeedback as ACK, and if a HARQ process is allocated to a deactivatedcell, or a HARQ process has not received any TB, or a HARQ process failsin decoding the received TB, the processor considers the first HARQfeedback as NACK. when the processor generates the second HARQ feedback,only if a HARQ process successfully decodes a received TB, the UEconsiders the second HARQ feedback as ACK, and if a HARQ process isallocated to a deactivated cell, or a HARQ process has not received anyTB, or a HARQ process fails in decoding the received TB, the processorconsiders the second HARQ feedback as NACK.
 14. A User Equipment (UE)operating in a wireless communication system, the UE comprising: a RadioFrequency (RF) module; and a processor configured to control the RFmodule, wherein the processor is configured to configure a first cellwith Physical Uplink Control Channel (PUCCH) resource and a second cellwith PUCCH resource, wherein the first cell and the second cell belongto an enhanced-NodeB (eNB), to configure zero or more third cellswithout PUCCH resource, wherein the zero or more third cells withoutPUCCH resource are associated with one of the first cell and the secondcell, to generate a first HARQ feedback by multiplexing HARQ feedbacksof all HARQ processes of the first cell and third cells associated withthe first cell, to generate a second HARQ feedback by multiplexing HARQfeedbacks of all HARQ processes of the second cell and third cellsassociated with the second cell, and to transmit the first HARQ feedbackon the first cell with PUCCH resource and the second HARQ feedback onthe second cell with PUCCH resource.
 15. The UE according to claim 14,wherein when the processor configures the first cell, the processorreceives an indication indicating which cells of the zero or more thirdcells without PUCCH resource are to be associated with the first cell.16. The UE according to claim 15, wherein when the processor configuresthe first cell, if the processor doesn't receive the indication, thefirst cell is not associated with any of the zero or more third cells.17. The UE according to claim 14, wherein when the processor configuresthe second cell, the processor receives an indication indicating whichcells of the zero or more third cells without PUCCH resource are to beassociated with the second cell.
 18. The UE according to claim 14,wherein when the processor configures a third cell among the zero ormore third cells, the processor receives an indication indicating whichcell with PUCCH resource is to be associated with the third cell. 19.The UE according to claim 18, wherein when the processor configures thethird cell among the zero or more third cells, if the processor doesn'treceive the indication, the third cell is associated with a Primary-Cell(PCell).
 20. The UE according to claim 14, wherein when the processormultiplexes the HARQ feedbacks of all HARQ processes of all cellsbelonging to the first PUCCH group, the processor considers HARQfeedback of a HARQ process of a cell belonging to the first PUCCH Groupas ACK (Acknowlegdement) if the HARQ process successfully decodes areceived TB (Transport Block), and the processor considers HARQ feedbackof a HARQ process of a cell belonging to the first PUCCH group as NACK(Negative-Acknowledgement) if the HARQ process is allocated to adeactivated cell, or a HARQ process has not received any TB, or a HARQprocess fails in decoding the received TB, and when the processormultiplexes the HARQ feedbacks of all HARQ processes of all cellsbelonging to the second PUCCH group, the processor considers HARQfeedback of a HARQ process of a cell belonging to the second PUCCH groupas ACK if the HARQ process successfully decodes a received TB, and theprocessor considers HARQ feedback of a HARQ process of a cell belongingto the second PUCCH group as NACK if the HARQ process is allocated to adeactivated cell, or a HARQ process has not received any TB, or a HARQprocess fails in decoding the received TB.